Metals and metallic alloys have metallic bonds consisting of metal ion cores surrounded by a sea of electrons. These free electrons which arise from an unfilled outer energy band allow the metal to have high electrical and thermal conductivity which makes this class of materials conductors. Due to the nature of the metallic bonds, metals and metallic alloys may exhibit a characteristic range of properties such as electrical and thermal conductivity. Typical metallic materials may exhibit values of electrical resistivity that generally fall in a range of between about 1.5 to 145 10−8 Ωm, with iron having an electrical resistivity of about 8.6 10−8 Ωm. Typical values of thermal conductivity for metallic materials may be in a range of between about 0.2 to 4.3 watts/cm ° C., with iron exhibiting a thermal conductivity of about 0.8 watts/cm ° C.
By contrast, ceramics are a class of materials which typically contain positive ions and negative ions resulting from electron transfer from a cation atom to an anion atom. All of the electron density in ceramics is strongly bonded resulting in a filled outer energy band. Ceramic alloys, due to the nature of their ionic bonding, will exhibit a different characteristic range of properties such as electrical and thermal conductivity. Because of the lack of free electrons, ceramics generally have poor electrical and thermal conductivity and are considered insulators. Thus, ceramics may be suitable for use in applications such as thermal barrier coatings while metals are not.
Designing a metal alloy to exhibit ceramic like electrical and thermal conductivities is unique. The only area where this has been utilized in material science is in the design of soft magnetic materials for transformer core applications. In such applications, extra silicon is added to iron in order to specifically reduce the electrical conductivity to minimize eddy current losses. However, iron-silicon alloys utilized for transformer cores typically contain a maximum of 2.5 at % (atomic percent) silicon because any additional silicon embrittles the alloy. Additionally, attempts to reduce electrical conductivity of iron transformer cores have not addressed reduced thermal conductivity.